Conrad and Kathy,
The water taxi situation is a bit up in the air now, with some of the boats planning on leaving from the Fort Point Tourist Village and others, the Caye Caulker Water Taxi boats, apparently staying at the Marine. That should all shake out in a couple of months.
But if you go are going to Caye Caulker, the CC Water Taxi boats are the way to go,as they have many departures a day to CC from the Marine Terminal. Just tell your taxi where you want to go and he'll drop you at the door of the Terminal. That part of town can be pretty busy, and sometimes there are some street hustlers around, but just go in, buy your ticket (US$7.50 to CC) and you can wait in the waiting room, which is an open-air room on the river in view of the famous Swing Bridge. If you have some extra time, you can go to one of the little museums in the Terminal. Or, if someone can watch your luggage, you can walk around Front Street. When the boat is ready to go, you'll have some help getting your luggage in. The CC Water Taxi boats hold maybe 25 people and are fast open boats usually with twin outboards.